Mixture control



Dec. 2, 1941. s. M. UDALE MIXTURE CONTROL Filed Aug. 15, 1938 INVENTORlocated the air pressure equalizing ring H.

yatehted 2, 1941 MIXTURE CONTROL Stanley M. Udale, Detroit, Michasslgnor to George M. Holley and Earl Holley Application August 15,1938, Serial No. 224,959

8 Claims.

The object of this invention is to improve the operation of an airplanecarburetor, so that the mixture ratio is correct for the followingvariables:

a. Temperature. b. The pressure in the air entrance leading to thecarburetor commonly known as the altitude correction. c. A correction tocorrespond to the variations of the air flow at given throttlepositions.

The specific form of carburetor to which this invention relates'is onein which two streamlined throttles form variable Venturi passages, oneon each side of a streamlined partition with which they both engage. Inthe throat of these variable venturis thus formed, fuel is dischargedfrom a passage located the streamlined partition. The discharge of thisfuel is controlled by a needle valve moved by a The two throttles andthe cam operating the needle valve are all geared together so that thqrmove together. By this means, as the throttle opens, the needle movesand the fuel orifice is opened.

Description In the air entrance ill of the carburetor is m. mediatelybelow is located the thermostatic needle l2. This needle contains a corewhich has a relatively high coefiicient of expansion (plastic materialsimilar to hard rubber). The result is that the needle point. M moves tothe left when the temperature increases and moves to the right when thetemperature decreases. This controls the flow of air through an orificeIE5 which is connected through a passage 96 to the chamber H which is incommunication with the piezometer ring H.

In the chamber i1 is also located the flexible 4 diaphragm 18 whichcarries the needle valve I 9. This diaphragm-forms the lower wall of thechamber 28 and a stamped wall cover 2| forms the upper portion. A spring22 is provided between the cover 2i and the flexible diaphragm i8; Thechamber 23 is evacuated so that the diaphragm 18 carries the fullatmospheric pressure and is supported by the spring 22. The movement ofthe needle valve I9 thus responds to changes in atmospheric pressure inthe air entrance and to supercharger pressure when used.

The air flowing by the needle valve 13 passes into a passage 23 intowhich also communicates the passage l5. There is a second chamber 24opening 26 which also admits atmospheric air into the passage 23. Themanual lever 21 controls the valve 28 which admits atmospheric air intothe passage 23. When the-lever 21 moves to the left, the opening 29 isclosed-and a lean mixture results. A rich mixture is obtained by movingthe lever 21 to the right when atmospheric pressure is freely admittedto the chamber 30. The passage 23, thus communicates through the passage29 with a chamber 30 which communicates with the passage 31 to the fuelneedle chamber 32, which surrounds.

the movable needle 33 which controls the fuel flow through the orifice33 which is located at the right hand end of a fuel passage 35, whichpassage communicates with the upper portion of the diaphragm chamber 36.

This diaphragm chamber 36 is provided with two diaphragms 3! and 38which operate the fuel needle shut off valves 39 and 40 throughmechanism of the standard type. These fuel needle valves 39 and 40 aresupplied with fuel through a high pressure fuel passage 41'. This highpressure fuel is derived from a fuel pump '42 which is provided with apressure control chamber 43 which permits excess fuel to be returned tothe fuel entrance M of the fuel pump 42. The result is there is asubstantially constant pressure in the pipe The fuel and air flow downthe fuel nozzle 45 and discharge into a horizontal passage 43 which isprovided with fuel and air outlets 41 which discharge into the throat ofthe variable venturi.

This variable venturi forms the throttle of the carburetor and is formedfrom the left wall 53 and the right well 49. These two walls are gearedtogether by means of gears indicated by broken lines and M. Engagingwith the gear Si is the throttle control gear 52 which carries 0 theneedle control cam 53 which operates the needle valve 33 through a wellknown mechanism, indicated by the lever 81, roller 82 and spring 84 andfulcrum 83.

The throttle walls 48 and 49 are provided with openings 54 and 55 sothat the pressure in back of the throttle walls 48 and 49 issubstantially that existing in the throat of the variable venturi. Thepressure. in the mixture outlet from the carburetor is measured in thechannel 56 which corresponds to the piezometer ring H except that thepassage 56 only extends at right angles to the plane of the drawing anddoes not surround the air entrance. There is a correin which is locateda needle 25 controlling an 55 sponding passage 51 on the left hand wallwhich will be connected with the passage 56 through a passage 1-66.

The pressure in the passages 56 and 51 is thus the pressure in themixture outlet. connected to the channels 56 and 51. A pipe 59 isconnected with the pressure existing back of the throttle wall 49. Thesetwo pipes 58 and 59 are operatively connected with two diaphragms 66 and8|. The upper diaphragm 6| moves the needle valve 25 and controls theadmission of atmospheric air past the valve 25 into the passage 23. Thisdiaphragm BI is enclosed between a stamping 62 and a second stamping 63.The movement of the needle valve 25 is controlled not only by thedifference of pressure in the two pipes 58 and 59, but also by a spring64 which seats inside the piston 65. This piston 65 engages with a cam66 whichis pivotally supported on the cover 63. The cam 66 is moved bylever 61 through a rod 68 which is connected with a throttle lever 69which is interconnected with operating gears 56, 52.

A similar mechanism is used to control the diaphragm 66 comprising a rod16 connected to the throttle lever 69. The rod- 16 is pivotallyconnected to a lever 1| which is rigidly connected with the cam 12 whichengages with the piston 13 which regualtes the compression in the spring14 which engages with the diaphragm 66. This diaphragm 66 engages withthe needle valve 15 which controls the flow through the opening 16,which admits fuel to the power jet 11 along with a certain amount of airwhich enters freely into the passage 85 leading to the power jet 11. Thepressure of the fuel that flows through the orifice 16 past the needle15 to the power jet 11 is controlled by the pressure in the diaphragmchamber 43 of the fuel pump 42. The pressure on the diaphragm in thechamber 43 is controlled by a spring 95 which is carried in the stamping96, which stamping is used to clamp in place the diaphragm 91. Thechamber formed between the diaphragms 96 and 91 communicates with thepiezometer ring through the pipe 98.

The needle valve 99 thus responds to the pressure in the air entrance l6and in the event that a supercharger is used, a higher pressure ismaintained on the diaphragm 91 and hence a higher pressure is maintainedin the pipe 4| and hence a higher flow takes place past the needle valve15 to the power jet 11. The reason for this detail is that the greaterthe density of the air, the leaner the mixture produced by the flow ofthe air through a given venturi. Hence an increase in density of air inthe air entrance I6 should be followed by an increase of pressure on thefuel in the passage 4|. 4

Considering next the structural details, the diaphragm 66 is mountedbetween the two stampings 86 and 81. Four diaphragm chambers are thusformed, 88 and 89 controlling the needle valve 15, just as chambers 96and 9| control the needle valve 25. These four chambers 88, 89, 96 and9| are connected together by pipes 92, 93, so that the pressure in thediaphragm chambers 88 and 96 corresponds to the pressure, or vacuumrather, in the throat of the variable venturi at the point 55. Thepressure in the diaphragm chambers 89, 9|, on the other hand, is thepressure, or vacuum, existing in the mixture outlet, or morespecifically, in the channels 56 and 51, assuming that 56 and 51 areconnected together by a passage I66.

A passage 94 connects the air chamber 36 Apipe58iswith a chamber |6|adjacent the gasoline diaphragm chamber 36.

The pressure or suction in the channel 3| is determined by the suctionin the chamber 32 which obtains air through a fixed opening 86 and froma variable opening 18 in the needle valve 33, which opening communicatesthrough I 19 with the air entrance l6.

The effect of the outlets 41 is that when the throttle is closed' and 18is open, the suction in chamber 32 is low; when the throttle is halfopen and 18 is closed the suction in 32 is high. When the throttle iswide open, the suction in 32 is again low. This variation of the suctionin the air chambers 36 and |6| depends, therefore, on throttle position.

The reason the nozzle 11 is supplied with fuel under high pressure andthe nozzle 41 under low pressure is that the fuel that issues from 41provides the normal requirements of the engine and the mixture ratiodetermined by the flow through the orifices 41 is substantiallyconstant. The fuel supply through the nozzle 11 is fuel that is requiredonly when the engine is developing its maximum horsepower, or withinthirty per cent of its maximum horsepower, in which range of power extrafuel is needed to prevent the engine overheating. It has been founddesirable to separate these two fuel supplies.

What I claim is:

1. An aircraft carburetor having an air entrance, two throttles locatedtherein, a mixture outlet, a fuel pump adapted to supply fuel under anapproximately constant pressure of a substantial amount, a fuel chamberhaving a diaphragm connected thereto, a diaphragm-operated fuel valvetherein adapted to reduce the fuel pressure to a relatively low head soas to supply fuel to.the carburetor, an air chamber associated with saiddiaphragm, the pressure therein being adapted to control said head, acarburetor mixing chamber located between the two throttles so as toform a variable mixing chamber therebetween, a combined air and fuelnozzle discharging into the throat of said variable air passage, a fuelpassage connecting the fuel diaphragm chamber with said fuel and airnozzle, a restricted air orifice communicating with said fuel and airentrance and connected so as to derive its air from said air entrance,an air passage connecting the air diaphragm chamber with said fuel andair nozzle, a second air passage leading out of the air entrance andcommunicating with the diaphragm air chamber, valve means associatedwith said air passages for controlling the pressure in said diaphragmair chamber at a pressure intermediate the pressure in the air entranceand the suction in the throat of the variable air passage, temperatureresponsive means operatively connected to said valve means and locatedin said air entrance so as to be responsive to the temperature of theflow of air therein whereby an increase in temperature in the airentrance reduces the pressure in said diaphragm air chamber byprogressively subjecting said diaphragm air chamber to the effect of thesuction in the throat of said variable air passage.

, 2. An aircraft carburetor having an air entrance, two throttleslocated therein, a mixture outlet, a fuel pump adapted to supply fuelunder an approximately constant pressure of a substantial amount, a fuelchamber having a diaphragm connected thereto, a diaphragm-operated fuelvalve therein adapted to reduce the fuel pressure to a relatively lowhead and to supply fuel tothe carburetor, an air chamber associated withsaid diaphragm, the pressure therein being adapted to control said head,a carburetormixing chamber located between the two 1 throttles so as toform a variable mixing chamber therebetween, a combined air and fuelnozzle discharging into said variable mixing chamher, a fuel passageconnecting the fuel diaphragm chamber with said fuel andair nozzle,

. a restricted air orifice communicating with said fuel and air nozzleand connected so as to derive its air from the air entrance, an airpassage connecting the diaphragm chamber with said fuel and air nozzle,a second air passage leading out of the air entrance and communicatingwith the diaphragm air chamber, valve means associated with said airpassages and adapted to control the pressure in said diaphragm airchamber at a the air flow therein, pressure responsive means operativelyconnected to said valve means and responsive to the atmospheric pressurein said air entrance also adapted to control the pressure in saiddiaphragm air chamber at a pressure intermediate the pressure in the airentrance and the suction in the throat, whereby an increase intemperature and a decrease in atmospheric pressure simultaneouslyincrease the influence of the suction in said air chamber and thusreduce the pressure therein by progressively subjectin said chamber tosaid suction.

3. An aircraft carburetor having an air entrance, a throttle locatedtherein, a mixture outlet, a fuel pump adapted to supply fuel under anapproximately constant pressure of a substantial amount, a fuel chamberhaving a diaphragm connected thereto, a diaphragm-operated fuel valvetherein adapted to reduce the fuel pressure to a relatively low head andto supply fuel to the carburetor, an air chamber associated with saiddiaphragm, the pressure therein being adapted to control said head, acarburetor mixing chamber located adjacent to the throttle which isadapted to create a variable mixing chamber between the throttle and thewalls of the air entrance, a combined air and fuel nozzle discharginginto said variable mixing chamber, a fuel passage connecting the fueldiaphragm chamber with said air and fuel nozzle, a restricted orificecommunicating with said air and fuel nozzle and adapted to obtain a suppy of air from said air entrance, an air passage connecting the airdiaphragm chamber with said fuel and air nozzle, a second air passageleading out of the air entrance and communicating with said diaphragmair chamber, valve means associated with said air passages and adaptedto control the pressure in said diaphragm air chamber at a pressureintermediate the pressure in the air entrance and the suction in thethroat of the variable mixing entrance.

4. In an airplane carburetor an air entrance, a throttle valve therein,a mixing chamber formed adjacent to and on the engine side of thethrottle, a fuel nozzle discharging therein, a fuel supply chamber, anair chamber associated therewith adapted to control the head on saidfuel in said chamber, a passage connecting the said air chamber with themixing chamber at the point of fuel discharge, a second passageconnecting the said air chamber with the air entrance, valve meansassociated with said air passages and adapted to control the pressure insaid air chamber at a pressure intermediate the pressure in the airentrance and the suction in the mixture chamber, temperature responsivemeans located in the air entrance and responsive to the temperature ofthe air in said air entrance connected to said valve.

5. In an airplane carburetor an air entrance, a throttle valve therein,a variable mixing chamber formed between the throttle and the walls ofthe air entrance, 9. fuel nozzle discharging therein, a

- fuel'supply chamber, an air chamber associated therewith adapted tocontrol the head on said the point of fuel discharge, a restriction insaid passage, a second passage from the air chamber leading into the airentrance on the atmospheric side of said throttle, valve means forregulating the relative effect of the atmospheric pressure in the airentrance and the suction in the variable mixing chamber, thermostaticmeans located in the air entrance adapted to control said valve wherebythe fuel mixture ratio is maintained constant independently oftemperature changes.

6. In an airplane carburetor an air entrance, a throttle valve therein,a mixing chamber formed adjacent to and on the engine side of thethrottle, a fuel nozzle discharging therein, a fuel supply chamber, anair chamber associated therewith adapted to .control the head on saidfuel in said chamber, a passage connecting the said air chamber with thevariable mixing chamber at the point'of fuel discharge, a second pasasgeconnecting thesaid air chamber with the air entrance, valve 'meansassociated with said air passage and adapted to control the pressure insaid air chamber at a pressure intermediate the pressure in the airentrance and the suction in the 'mixture chamber, pressure responsivemeans responsive to the atmospheric pressure in the air entranceconnected to said valve means, temperature responsive means located inthe air entrance and responsive to the temperature of the air in saidair entrance also connected to said valve means.

7. In an airplane carburetor an air entrance, a throttle valve therein,a mixing chamber formed adjacent to and on the engine side of thethrottle, a fuel nozzle discharging therein having a restricted fuelentrance and an enlarged outlet, a fuel supply chamber, an air chamberassociated therewith adapted to control the head on said fuel in saidchamber, a restricted air passage connecting said air entrance to theenlarged fuel outlet, a second passage leading from said enlarged fueloutlet to said air chamber so as to subject said chamber to the suctionin the mixing chamber at the point of fuel discharge, a third passageconnecting said air chamber with the air entrance, valve meansassociated with said air passage and adapted to control the pressure insaid air chamber at a pressure intermediate the pressure in the airentrance and the suction in the mixture chamber, temperature responsivemeans located in the air entrance and responsive to the temperature ofthe air flowing A through said air entrance connected to said valve.

8. In an airplane carburetor an air entrance, a throttle valve therein,a mixing chamber located adjacent to and on the engine side of thethrottle, a fuel nozzle discharging therein having a restricted fuelentrance and an enlarged outlet, a fuel supply chamber, an air chamberassociated therewith adapted to control the head on said fuel in saidchamber, a restricted air passage connecting the last air entrance tothe enlarged fuel outlet, 9. second passage leading from said enlargedfuel outlet to said air chamber so as to subject said chamber to thesuction in the mixing chamber at the point of fuel discharge, a thirdair passage connecting said air chamber with the air entrance, valvemeans associated with said air passage and adapted to control thepressure in said air chamber at a pressure intermediate the pressure inthe air entrance and the suction in the mixing chamber, pressureresponsive means responsive to the' atmospheric pressure in the airentrance connected to said valve means, temperature responsive meanslocated in the air entrance and responsive to the temperature oi the airflow through said air entrance also connected to said valve means.

- STANLEY M. UDALE

